1. Technical Field
The invention relates to manually applying drops to human eyes, more particularly, a manual eye drop applicator and a method to insert a drop of liquid into the eye.
2. Background
Using eye droppers to insert drops into an eye to alleviate various conditions has been known for a long time. The human eye is subject to several maladies, some of which can be treated with the topical application of medicaments. For example, bacterial conjunctivitis, a/k/a “pink eye” (as opposed to the viral form) can be treated with antibacterial solutions. Keratoconjunctivitis sicca, a/k/a “chronic dry eyes” can be ameliorated with artificial tears. Various eye irritations can be treated with artificial tears or other solutions.
In these cases, the object is to get at least some of the solution into the lower conjunctival sac, the space between the sclera and lower eye lid. Since the solutions are not expensive, wasted drops that run down the check are not a major concern.
A much more serious affliction is glaucoma. In the most common forms, this manifests as a buildup of pressure inside the eye between the lens and retina. If left untreated, the optic nerve can be damaged leading to eventual blindness. The usual treatment is to apply one or more medicaments in the form of eye drops. In this case, the cost of wasted drops can become significant. Moreover, prescriptions are based on an assumed dosage of one drop per application and wastage may require premature prescription renewal. Insurance coverage can be an issue. Lastly, most glaucoma medicines have side effects and inadvertent overdosing, though usually limited by conjunctival sac capacity, is not desirable.
Over the counter solutions are generally used on an as needed basis to alleviate a condition that is perceived by the user. Successful drop application often provides some immediate relief. In the case of glaucoma, the drops do not provide any felt relief. However, to prevent further loss of vision, they must be applied two or more times every day for life.
Over the years, a preferred method has been developed for patient administration of medicated drops. Some time ago, bottles with separate glass eye droppers gave way to integral plastic bottles. These are small hand held pliable containers with cone shaped nozzles of varying inner diameters. Inverting the container and squeezing it causes drops to come out. The size of the drop depends on the solution, nozzle diameter and bottle tilt angle.
“How to put in your eye drops” from the NIH Clinical Center is typical patient advice: 1) wash hands to prevent eye infections, 2) hold the bottle in one hand (the right for right-handed people), 3) either lie down or tip the head back so the eye is looking up, 4) use the index finger of the other hand to pull down the lower lid to form a pocket, and 5) hold the bottle over the eye and squeeze so that a drop falls onto the eye.
While this seems straightforward, it is difficult for a large number of patients to perform consistently well. Most people have a blink reflex which makes it difficult to keep the eye open when viewing a close-in object. Glaucoma generally affects those of advanced age. Often, their manual dexterity is compromised making it hard for them to squeeze out a single drop of an appropriate size, if they can do so at all. Aiming the bottle so that a drop falls into the eye instead of on an eyelid or cheek is a problem for some. As a result, studies have shown that noncompliance with prescribed treatments has proven to be a significant obstacle to effective glaucoma management.
For example, Winfield et al. (1990) undertook a study of the causes of non-compliance and reviews the findings of earlier teams (footnoted) between 1982 and 1986. Problems include missed doses, inability to place drops in eyes, a wide variation in drop size from commercial droppers, and difficulty in aiming. Several aids are mentioned that were available in 1985, generally directed to aiming. This study enrolled patients (ages 9-92) taking drops for glaucoma (32%), post-surgical (25%), dry eyes (10%), irritation (10%), balance other. Administration was by means of a dispenser bottle aimed at the eye. They found that 57% had some difficulty, poor aim being the major problem with difficulty squeezing the bottle and blinking next. The authors proposed a bottle holding appliance with a stabilizer surrounding the eye socket.
Although not a compliance study, problems were apparent even earlier. Fraunfelder (1976) used radioactive technetium as a tracer to study the fluid dynamics of applied topical medication to determined how best to apply it. He notes that commercial eyedroppers produce 50-75 uL drops and are much too large, since they produce a blink reflex which washes away most of it. Based on what the conjunctival sac can hold after blinking, a drop size of 13 uL is recommended.
Salyani et al. (2005) stated that “Methods to improve patient compliance with prescribed topical use of glaucoma medication are sorely needed.” They evaluated patient use of a three part eye drop guide comprising a transparent plastic inverted funnel that fit over a bottle. Apparently, it proved difficult to wash and was not worth the effort for experienced users. Newsom (2008), in his advice on How to Put in Eye Drops, states that “many people find taking drops difficult,” but shows two drop aids. Xalease and Opticare appear to be combination bottle squeezer and eye socket alignment guides.
The problem is still not solved. Connor & Severn (2011), in a study of bottle force requirements, summarize earlier studies: “Non-compliance in glaucoma and ocular hypertension is common.” “At least 50% of patients report difficulty in self-administration. The two most common frequently reported causes of difficulty include aiming a bottle and squeezing a bottle.” Currently, they opine: “The insidious nature of disease progression and necessity for long-term therapy are key issues. In these conditions, the ease of topical delivery is of paramount importance.”
Thus, it is clear that, for a very long time, there has been a desperate need for an advance over an eyedropper bottle.
Some patents have also addressed similar problems. Below are uncritical thumbnail sketches using the inventor's terminology as much as possible in approximate date order. Even if some of these patents are not analogous art, they do provide a historical perspective. Of course, searching is not foolproof and there may be other more relevant patents not found or inadvertently glossed over.
U.S. Pat. No. 4,036,230 to Adams on Jul. 19, 1977, titled, “Medicinal Insert Instrument,” is concerned with a swab-like device that places and removes plastic inserts that provide timed-release medication to the eye.
U.S. Pat. No. 4,913,682 to Shabo on Apr. 3, 1990 (Division of U.S. Pat. No. 4,838,851, Jun. 13, 1989), titled, “Applicator and Package Thereof,” compromises a handle and an absorbent tip for scrubbing an eyelid.
U.S. Pat. No. 5,040,706 to Davis et al. on Aug. 20, 1991, titled, “Liquid Drop Dispensing Apparatus,” comprises a hollow compressible body connected to a nozzle at approximately 90°. The nozzle discharge passage is sized to produce a liquid drop of predetermined size when the body is squeezed. Advantages include not having to tilt the head back and being able to use one hand to hold the lower eyelid down while squeezing the body with the other.
U.S. Pat. No. 5,516,008 to Rabenau et al. on May 14, 1996, titled, “Medication Dispensing Container,” replaces the conventional squeeze bottle with a small capacity storage cavity having a flexible top wall which can be squeezed. A discharge nozzle is at an approximately right angle to the cavity housing body. Problems overcome include sterilization and plastic manufacturing which can result in rough edge eye hazards.
U.S. Pat. No. 5,888,005 to Gueret on Mar. 30, 1999, titled, “Capillary Dosing unit with Terminal Slit,” is directed to the unrelated field of applying dermopharmaceuticals to the nails, eyelids, or other parts of the face or scalp. A flexible hand-held applicator has a cylindrical end with a slit along a diameter that acts as a capillary reservoir after dipping into a solution. Dosing depends on capillary volume since excess can be wiped off inside a dispenser bottle.
U.S. Pat. No. 5,665,079 to Stahl on Sep. 9, 1997, titled, “Eye Drop Dispenser Including Slide,” provides a slide to which a conventional eye drop squeeze bottle may be attached. Drops squeezed into a channel on the slide roll into the eye. This allows upright application and overcomes the blink reflex of an overhead bottle.
U.S. Pat. No. 6,041,978 to Hagele on Mar. 28, 2000, titled, “Liquid Dropper for Upright Eye Drop Instillation,” comprises a squeeze bottle reservoir with a conduit having a delivery end at right angles to the squeeze bottle axis. Inside the conduit, is a rod which culminates in a ball that collects liquids from the conduit forming drops that fall into the eye. The major problem solved is to allow the head to remain upright without the drawbacks of the prior art which did not well direct drops into the eye.
U.S. Pat. No. 6,869,421, issued to Hanley on Mar. 22, 2005, titled, “Device for Non-Gravity Presentation of Liquid Droplet.” Liquid is held in a squeeze bottle that communicates via one or more capillary tubes to an eye presentation surface. Drops on the presentation surface are held in place by liquid in the capillary until the device is tilted past some critical angle, at which point the drop is no longer retained on the presentation surface. It is averred that the critical angle may be 90° if several capillary tubes are used.
U.S. Pat. No. 7,374,559 to Berger et al. on May 20, 2008, titled, “Hand-held Device Enabling Accurate Dispensing of a Drop of Liquid into the Eye of a Subject,” comprises a funnel connected via a curving capillary tube to a discharge outlet.
U.S. Pat. No. 7,527,613 to Gaynes on May 5, 2009, titled, “Therapeutic Solution Drop Dispenser,” proposes a reservoir and a dispensing tip, having various features including removable apertures, at a non-zero angle, theta, to the reservoir portion. It is averred that the dispenser allows keeping the head upright with the dispenser portion horizontal. Apparently, one problem is that prior art drop size depended on the angle of administration. The dispenser tip apertures allow control of drop size in the range of 1 μL to 50 μL.
U.S. Pat. No. 7,846,140 to Hagele on Dec. 7, 2010, titled, “Mini Eye Drop Tip,” proposes attaching a mini tip dispenser to existing eye dropper bottles to produce a drop that is smaller than typical. The tip is flexible to prevent eye damage on accidental contact.
Japanese published application, P2006-116071A on May 11, 2006 by Tsubota, titled, “Instrument for Administering an Ophthalmic Drug,” relates to administering medicine in the form of solid or semi-solid ointments to an inner eyelid, apparently by an ophthalmologist, to treat dry eye. A spatula-like instrument with a long narrow body and a drug support part with a depression at one end is disclosed. Many materials may be used in construction, but glass or hard plastic is especially preferred, albeit with a rounded end to prevent accidental damage to the cornea. According to the inventor, it is difficult to use a liquid drug with high fluidity or volatility.
As far as is known, none of the inventions related to applying liquid drops to the eye have met with commercial success. The majority of patients are still stuck using an eye dropper bottle with its attendant difficulties.